1. Field of the Invention
The present invention relates to a liquid crystal display and a signal correcting circuit therefor, and, more particularly, to an active matrix type liquid crystal display and a signal correcting circuit therefor.
2. Description of the Related Art
Conventional liquid crystal displays suffer generation of residual images at the time of displaying moving pictures because the response speeds have not reached the level that matches with the display of TV images. In particular, an in-plane switching (IPS) active matrix type liquid crystal display is disadvantageously likely to generate residual images.
To prevent such image persistence, many conventional IPS liquid crystal displays use a so-called low-resistant liquid crystal whose material has a reduced specific resistance (see Japanese Patent Laid-Open No. 159786/1995). While the response of this conventional IPS liquid crystal display that uses a low-resistant liquid crystal is improved by reducing the specific resistance of the liquid crystal material, a voltage is applied to the liquid crystal panel without correcting image signals.
In case where an image with high contrast should move within the screen, however, only a unidirectional electric field would be generated between the pixel electrodes of such a conventional liquid crystal display. This caused concentration of charges only on one of the pixel electrodes which are opposing each other. This charge concentration brought about display problems, such as generation of residual images and flickering of the screen.
Referring now to FIGS. 1A to 1C and 2, the cause for the concentration and storage of charges only on one of the pixel electrodes which are opposing each other will be described below. FIG. 1A shows how, for example, a monochromatic vertical stripe image having high contrast moves across the background of an intermediate tone. In case where white and black portions of such an image move rightward frame by frame (a time unit in which all the pixels that constitute one screen of the display panel are scanned) as shown in FIG. 1B, a voltage to be applied to the liquid crystal frame by frame becomes as shown in FIG. 1C. In FIG. 1C, (1) to (5) indicate display positions in which the image moves rightward frame by frame.
FIG. 2 shows the behavior of an electric field between the pixel electrodes (the pixel electrode and the opposing electrode opposing to said pixel electrode) and when the voltage as shown in FIG. 1C is applied to the liquid crystal. In the frames (1) and (3), the voltage on the pixel electrode is higher than the voltage on the opposing electrode, so that charges are concentrated only on the pixel electrode and are stored there. Because an electric field is not generated in each of the frames (2) and (4), however, charges are not stored. Although an electric field is generated after the frame (5), the direction of the electric field is reversed symmetrically frame by frame, so that charges are not stored. As a result, the charges stored in the pixel electrode in the frames (1) to (5) influence the display while they are diffused, thus causing undesirable generation of residual images and flickering of the screen.